Polymeric colored materials generally exhibit a high degree of solubility and excellent colorability when employed in hydrocarbon compositions such as mineral oils, fuels and the like, and in wax compositions, such as candles, crayons and the like. However, colored polymers are not disclosed in the prior art as dispersing agents for use hydrocarbon compositions or printing inks. For example, U.S. Pat. No. 6,187,085 B1 describes a printing ink composition made of carbon black and an alkali metal hydroxide in combination with an alkenyl succinimide for dispersing the carbon black. It also discloses a method of dispersing carbon black in a mineral oil and metal salts, which exhibit poor lithographic printing performance. U.S. Pat. No. 6,508,873 B1 discloses phthalocyanine polymeric amides and esters with a polymeric tail of up to C30 for use as colorants in ink-jet printing inks. U.S. Pat. Nos. 6,451,071 and 6,287,348 disclose colored materials of the structure A-B—X wherein A is an organic chromophore, B is an electrophilic linking group bonded to A, and X is selected from the group of C12-C24 primary or secondary amines. U.S. Pat. No. 6,486,248 B2 discloses a hydrocarbon soluble liquid polymeric colorant comprised of a chromophore and oleophilic binder and an alcohol including a carbon chain between C3-C30. U.S. Pat. No. 6,452,020 B1 discloses xanthene colorants that exhibit improved wax or oil solubility made with polyoxyalkylene polymers. U.S. Pat. No. 6,106,597 discloses a polymeric colorant with the formula R{A[(B)nR1]m}x wherein R is an organic chromophore, A is a linking group, B is a C2-C4 alkyleneoxy constituent, n is an integer from 2-100, m is 1 when A is O, S, CO2 or 2 when A is N or SO2N, x is an integer from 1-5 and R1 is a C8-C20 fatty acid. U.S. Pat. No. 6,034,158 discloses a colorant wax composition comprising a colorant of the formula R{A-[(alkyleneoxy constituent)nN}m}x wherein R is an organic chromophore, A is a linking group, B is a C2-C4 alkyleneoxy constituent, n is an integer from 2-100, m is 1 when A is O, S, CO2 or 2 when A is N or SO2N, x is an integer from 1-5 and a surfactant selected from the group consisting of a derivative of sorbitan monooleate. U.S. Pat. No. 6,022,944 discloses a polymeric colorant of the structure A[SO2N(R1)—(Y)]1-6 where A is an anthraquinone chromophoric radical, Y is a polymeric substituent having from 4-200 repeat groups and R1 is selected from H, Y, C1-12, or alkyl, aryl or cycloalkyl. U.S. Pat. No. 5,789,515 discloses a colorant with the structure ABXYZ in which A is an organic chromophore, B is an electrophilic reactive group covalently bonded to A, X is a nucleophilic linking group covalently bonded to B, Y is a poly(oxyalkylene)-polysiloxane copolymer, and Z is a terminal group for Y. U.S. Pat. No. 5,766,268 discloses a colorant compatible with polar solvent colorants with the structure ABXYZ in which A is an organic chromophore, B is an electrophilic reactive group covalently bonded to A, X is a nucleophilic linking group covalently bonded to B, Y is a poly(oxyalkylene) polymer, and Z is a terminal group for Y. U.S. Pat. No. 5,270,363 discloses a phthalocyanine colorant that contains polyoxyalkylene polymeric tails. U.S. Pat. No. 5,177,200 discloses a colorant of the formula A—(SO2—N(R2)—Yn wherein A is a non-ionic metalophthalocyanine chromophore of Cu, Ni, or Al, R2 is a hydrogen C1-C6 alkyl or cycloalkyl, phenyl, benzyl, or Y, Y is a poly(oxyalkylene) moiety comprising 3 units, and n is an integer between 1-4. U.S. Pat. Nos. 5,419,800 and 5,135,972 both disclose a phthalocyanine colorants that contain polyoxyalkylene polymeric tails. U.S. Pat. No. 4,141,684 discloses a colorant that is a chromophore covalently bonded to a polyalkylene oxides of a molecular weight of at least 500 amu. U.S. Pat. No. 4,137,243 discloses anthraquinone polymeric colorants that contain polyoxyalkylene polymeric tails. U.S. Pat. No. 5,100,471 discloses an aqueoU.S. ink jet composition comprised of a solvent and colored particles having a polymeric core and a silica shell onto which dyes are covalently bonded. U.S. Pat. No. 4,468,255 claims diazo and azo linkage Schiff's bases reacted with polyoxyalkane polymeric chains which can be used as a rheological modifier for pigment dispersions.
As indicated hereinabove, the prior art discloses polymeric colored materials that either have no more than C24 a polyalkene chain or contain a polyoxyalkylene polymer. However these polymeric colored materials are not suitable for use as pigment dispersants in non-polar systems and would not decrease the viscosity of a pigment dispersion when employed in a relatively small amount (i.e., 1-15% w/w pigment).
Thus there exists a need for a dispersant which lowers the viscosity of a pigment dispersion yet permits a higher pigment loading resulting in highly pigmented concentrations capable of being satisfactorily handled and dispersed in lithographic printing inks. Moreover, there exists a need to improve the stability of pigment dispersions used to pigment hydrocarbon compositions. There also exists a need for a dispersant that lowers the viscosity of highly concentrated non-polar pigment dispersions. At a high pigment load offering good lithographic and gravure printing performance while reducing the tendency towards scumming, feedback and over-emulsification.